Lighting apparatus using organic light emitting diode

ABSTRACT

An organic light emitting diode comprises an anode; an organic layer disposed on the anode and including a plurality of phosphorescent light emitting layers; and a cathode disposed on the organic layer, wherein a phosphorescent light emitting layer having a highest degree of horizontal orientation of a dopant among the plurality of phosphorescent light emitting layers is disposed to be adjacent to the cathode, and wherein the anode includes a short reduction pattern which implements a narrow path.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of Korean Patent Application No.10-2018-0166018 filed on Dec. 20, 2018, which is hereby incorporated byreference in its entirety.

BACKGROUND Field of the Disclosure

The present disclosure relates to a lighting apparatus using an organiclight emitting diode, and more particularly, to a lighting apparatususing an organic light emitting diode with improved luminous efficiency.

Description of the Background

Currently, fluorescent lamps or incandescent lamps are mainly used aslighting apparatuses. Among them, the incandescent lamps have a goodcolor rendering index (CRI) but have very low energy efficiency.Further, the fluorescent lamps have good efficiency, but have a lowcolor rendering index and contain mercury, which may cause anenvironmental problem.

The color rendering index is an index representing color reproduction.In other words, the color rendering index represents how much a feelingof a color of an object illuminated by a specific light source issimilar to a feeling of a color of the object illuminated by a referencelight source. A CRI of sunlight is 100.

In order to solve the problems of the lighting apparatus of the relatedart, recently, a light emitting diode (LED) is suggested as a lightingapparatus. The light emitting diode is formed of an inorganic lightemitting material. Luminous efficiency of the light emitting diode isthe highest in the red wavelength range and the luminous efficiencythereof is lowered toward a red wavelength range and a green wavelengthrange which has the highest visibility. Therefore, there is adisadvantage in that when a red light emitting diode, a green lightemitting diode, and a blue light emitting diode are combined to emitwhite light, the luminous efficiency is lowered.

As another alternative, a lighting apparatus using an organic lightemitting diode (OLED) has been developed. The organic light emittingdiode is configured by an anode, a plurality of organic layers, and acathode which are sequentially formed on a substrate.

However, light emitted from the plurality of organic layers is trappedat an interface of the plurality of organic layers and the cathode andis partially decayed, which results in the lowering of the luminousefficiency of the lighting apparatus.

SUMMARY

An object to be achieved by the present disclosure is to provide alighting apparatus using an organic light emitting diode with improvedluminous efficiency.

Another object to be achieved by the present disclosure is to provide alighting apparatus using an organic light emitting diode in which lightlost at the interface of the organic layers and the cathode isminimized.

Objects of the present disclosure are not limited to the above-mentionedobjects, and other objects, which are not mentioned above, can beclearly understood by those skilled in the art from the followingdescriptions.

In order to solve the above-described problems, according to an aspectof the present disclosure, a lighting apparatus uses an organic lightemitting diode, the organic light emitting diode comprises: an anode; anorganic layer disposed on the anode and including a plurality ofphosphorescent light emitting layers; and a cathode disposed on theorganic layer, wherein a phosphorescent light emitting layer having ahighest degree of horizontal orientation of a dopant among the pluralityof phosphorescent light emitting layers is disposed to be adjacent tothe cathode, wherein the anode includes a short reduction pattern whichimplements a narrow path. Therefore, the emission efficiency of thelighting apparatus may be improved.

According to another aspect of the present disclosure, a lightingapparatus uses a three-stack tandem type organic light emitting diode, afirst stack adjacent to a transparent electrode includes a greenphosphorescent light emitting layer, a third stack adjacent to areflective electrode includes a red phosphorescent light emitting layer,and a second stack disposed between the first stack and the third stackincludes a blue fluorescent light emitting layer. Therefore, theemission efficiency of the lighting apparatus may be improved.

Other detailed matters of the exemplary aspects are included in thedetailed description and the drawings.

According to the present disclosure, a phosphorescent light emittinglayer having a high degree of horizontal orientation is disposed to beadjacent to a reflective electrode to minimize a surface plasmonpolariton loss, thereby improving luminous efficiency of a lightingapparatus.

The effects according to the present disclosure are not limited to thecontents exemplified above, and more various effects are included in thepresent specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view illustrating a lighting apparatus usingan organic light emitting diode according to an exemplary aspect of thepresent disclosure;

FIG. 2 is a cross-sectional view illustrating a stack structure of anorganic layer according to an exemplary aspect of the presentdisclosure;

FIG. 3A is a front view of a lighting apparatus using an organic lightemitting diode according to an exemplary aspect of the presentdisclosure;

FIG. 3B is an enlarged view of a lighting unit of a lighting apparatususing an organic light emitting diode according to an exemplary aspectof the present disclosure;

FIG. 4 is a cross-sectional view taken along line I-I′ of FIG. 3A;

FIG. 5 is a view for explaining a relationship of a degree of horizontalorientation of a dopant and a light loss at an interface of an organiclayer and a second electrode; and

FIG. 6 is a graph illustrating luminous efficiency depending on adistance between an organic light emitting layer and a second electrode.

DETAILED DESCRIPTION

Advantages and characteristics of the present disclosure and a method ofachieving the advantages and characteristics will be clear by referringto exemplary aspects described below in detail together with theaccompanying drawings. However, the present disclosure is not limited tothe exemplary aspects disclosed herein but will be implemented invarious forms. The exemplary aspects are provided by way of example onlyso that those skilled in the art can fully understand the disclosures ofthe present disclosure and the scope of the present disclosure.Therefore, the present disclosure will be defined only by the scope ofthe appended claims.

The shapes, sizes, ratios, angles, numbers, and the like illustrated inthe accompanying drawings for describing the exemplary aspects of thepresent disclosure are merely examples, and the present disclosure isnot limited thereto. Like reference numerals generally denote likeelements throughout the specification. Further, in the followingdescription of the present disclosure, a detailed explanation of knownrelated technologies may be omitted to avoid unnecessarily obscuring thesubject matter of the present disclosure. The terms such as “including,”“having,” and “consist of” used herein are generally intended to allowother components to be added unless the terms are used with the term“only”. Any references to singular may include plural unless expresslystated otherwise.

Components are interpreted to include an ordinary error range even ifnot expressly stated.

When the position relation between two parts is described using theterms such as “on”, “above”, “below”, and “next”, one or more parts maybe positioned between the two parts unless the terms are used with theterm “immediately” or “directly”.

When an element or layer is disposed “on” another element or layer,other layer or element may be interposed therebetween.

Although the terms “first”, “second”, and the like are used fordescribing various components, these components are not confined bythese terms. These terms are merely used for distinguishing onecomponent from the other components. Therefore, a first component to bementioned below may be a second component in a technical concept of thepresent disclosure.

Like reference numerals generally denote like elements throughout thespecification.

A size and a thickness of each component illustrated in the drawing areillustrated for convenience of description, and the present disclosureis not limited to the size and the thickness of the componentillustrated.

The features of various aspects of the present disclosure can bepartially or entirely adhered to or combined with each other and can beinterlocked and operated in technically various ways, and the aspectscan be carried out independently of or in association with each other.

Hereinafter, a light apparatus according to exemplary aspects of thepresent disclosure will be described in detail with reference toaccompanying drawings.

FIG. 1 is a cross-sectional view illustrating a lighting apparatus usingan organic light emitting diode according to an exemplary aspect of thepresent disclosure.

In the present disclosure, provided is a lighting apparatus using anorganic light emitting diode formed of an organic material, rather thana lighting apparatus using an inorganic light emitting diode formed ofan inorganic material.

Luminous efficiency of green and red light of the organic light emittingdiode formed of an organic light emitting material is relatively betterthan that of an inorganic light emitting diode. Further, the organiclight emitting diode has a relatively wider width of an emission peak ofred, green, and blue light as compared with the inorganic light emittingdiode, so that the color rendering index (CRI) is improved so that thelight of the lighting apparatus is more similar to the sunlight.

Referring to FIG. 1, a lighting apparatus 100 using an organic lightemitting diode according to an exemplary aspect of the presentdisclosure includes an organic light emitting diode unit 110 whichperforms surface emission and an encapsulating unit 120 whichencapsulates the organic light emitting diode unit 110.

Specifically, the organic light emitting diode unit 110 may sequentiallyinclude a substrate 111, an internal light extracting layer 112, aplanarizing layer 113, a barrier layer 114, a first electrode 115, anorganic layer 116, and a second electrode 117 from the lower side.

An external light extracting layer 118 for increasing a haze may beadditionally provided above the organic light emitting diode unit 110.However, the present disclosure is not limited thereto and the lightingapparatus 100 of the present disclosure may not include the externallight extracting layer. Here, the external light extracting layer 118 isconfigured such that scattering particles such as TiO₂ are dispersed ina resin and may be attached above a substrate 111 by means of anadhesive layer (not illustrated).

In addition, as it will be described below with reference to FIGS. 3Band 4, the organic light emitting diode unit 110 may further include anauxiliary line AL for compensating conductivity of the first electrode115 and an insulating layer INS for suppressing the short of the firstelectrode 115 and the second electrode 117.

The substrate 111 may be formed of a transparent glass. Further, thesubstrate 111 may be formed of a polymer material having flexibilitysuch as polyimide.

Here, the organic layer 116 which emits light and the first electrode115 and the second electrode 117 which are disposed on and below theorganic layer 116 to supply charges to the organic layer 116 may form anorganic light emitting diode (OLED).

For example, the first electrode 115 may be an anode which suppliesholes to the organic layer 116 and the second electrode 117 may be acathode which supplies electrons to the organic layer 116, but are notlimited thereto and the functions of the first electrode 115 and thesecond electrode 117 may be switched.

Generally, the first electrode 115 may be formed of indium tin oxide(ITO) or indium zinc oxide (IZO) which is a transparent metal oxidematerial having a high work function and good conductivity or a thinmetal film to easily inject the holes. Here, a specific example of thethin metal film may be formed of a metal such as magnesium (Mg), calcium(Ca), sodium (Na), titanium (Ti), indium (In), yttrium (Y), lithium(Li), gadolinium (Gd), aluminum (Al), silver (Ag), tin (Sn) and lead(Pb), or an alloy thereof. The first electrode 115 may be configured bya single stack or may also be configured by a multi-stack formed of theabove-mentioned materials.

Further, the second electrode 117 is desirably formed of a conductivematerial having a low work function so as to easily inject electrons tothe organic layer 116. A specific example of a material used for thesecond electrode 117 may be formed of a metal such as magnesium (Mg),calcium (Ca), sodium (Na), titanium (Ti), indium (In), yttrium (Y),lithium (Li), gadolinium (Gd), aluminum (Al), silver (Ag), tin (Sn), andlead (Pb), or an alloy thereof. The second electrode 117 may also beconfigured by the single stack and configured by the multi-stack formedof the above-mentioned materials.

The organic layer 116 may be formed with a multi-stack tandem structureto improve luminous efficiency. Specifically, the organic layer 116 maybe formed with a multi-stack tandem structure including a red organiclight emitting layer EML, a green organic light emitting layer EML, anda blue organic light emitting layer EML.

Further, each stack of the organic layer 116 may include an electroninjection layer EIL and a hole injection layer HIL which injectelectrons and holes to the organic light emitting layer EML,respectively, and an electron transport layer ETL and a hole transportlayer HTL which transport the injected electrons and holes to the lightemitting layer, respectively, and a charge generating layer CGL whichgenerates charges such as the electrons and the holes. A detailedstructure thereof will be described below with reference to FIG. 2.

When a current is applied to the first electrode 115 and the secondelectrode 117, the electrons are injected from the second electrode 117to the organic layer 116 and holes are injected from the first electrode115 to the organic layer 116. Thereafter, excitons are generated in theorganic layer 116. As the excitons are decayed, light corresponding toan energy difference of a lowest unoccupied molecular orbital (LUMO) anda highest occupied molecular orbital (HOMO) of the light emitting layeris generated.

Here, it is determined whether the light generated in the organic layer116 is emitted through the front surface or through the rear surfacedepending on transmittance and reflectance of the first electrode 115and the second electrode 117.

In the exemplary aspect of the present disclosure, as described above,the first electrode 115 is a transparent electrode and the secondelectrode 117 is used as a reflective electrode. Therefore, the lightemitted from the organic layer 116 is reflected by the second electrode117 to be transmitted through the first electrode 115 so that the lightis generated to the lower portion of the organic light emitting diodeunit 110. That is, the organic light emitting diode unit 110 accordingto an exemplary aspect of the present disclosure may perform bottomemission.

However, the present disclosure is not limited thereto and the firstelectrode 115 may be used as a reflective electrode and the secondelectrode 117 may be used as a transparent electrode so that the organiclight emitting diode unit 110 may perform top emission.

Further, the barrier layer 114 is disposed below the first electrode 115to block moisture, air, or fine particles penetrating from the substrate111 and the internal light extracting layer 112.

In order to suppress the penetration of moisture and air, the barrierlayer 114 may include a plurality of inorganic barrier layers and inorder to block the fine particles, the barrier layer 114 may include aplurality of organic barrier layers.

Specifically, the inorganic barrier layer may be formed of one of Al₂O₃,ZrO₂, HfO₂, TiO₂, ZnO, Y₂O₃, CeO₂, Ta₂O₅, La₂O₅, Nb₂O₅, SiO₂, and SiNT),which are inorganic insulating materials. The organic barrier layer maybe formed of acrylic resin or epoxy resin, and specifically, may beformed of photoacryl (PAC).

The internal light extracting layer 112 is disposed between thesubstrate 111 and the barrier layer 114 to increase the externalextracting efficiency of the light generated from the organic lightemitting diode which performs the bottom emission.

The internal light extracting layer 112 inserts titanium oxide TiO₂particles into a resin to increase internal light scattering and surfaceroughness, thereby increasing optical extraction efficiency.Specifically, the internal light extracting layer 112 may be formed tohave a thickness of 450 nm by an inkjet-coating method and a diameter oftitanium oxide TiO₂ particle may be 200 nm to 300 nm. However, thespecific value may vary to various values depending on the necessity ofthe design of the lighting apparatus 100.

The planarizing layer 113 is disposed on the internal light extractinglayer 112 to compensate the surface roughness of the internal lightextracting layer 112, thereby improving the reliability of the organiclight emitting diode unit 110.

The planarizing layer 113 is configured by inserting zirconia particlesinto a resin and compensates the surface roughness of the internal lightextracting layer 112. Specifically, the planarizing layer 113 may beformed by the inkjet-coating method to have a thickness of 150 nm and adiameter of the zirconia particle may be 50 nm. However, the specificvalue may vary to various values depending on the necessity of thedesign of the lighting apparatus 100.

The encapsulating unit 120 covers the organic light emitting diode unit110 to protect the organic light emitting diode unit 110 by blocking theinfluence from the outside. The encapsulating unit 120 includes anadhesive layer 121 which is in contact with the organic light emittingdiode unit 110, a metal film 122 which is in contact with the adhesivelayer 121, and a protective film 123 attached onto the metal film 122.

The adhesive layer 121 may be formed of a pressure sensitive adhesive(PSA) which bonds the metal film 122 and the organic light emittingdiode unit 110. A thickness of the adhesive layer 121 may be 30 □ m butis not limited thereto and may vary to various values depending on thenecessity of the design of the lighting apparatus 100.

The metal film 122 is disposed on the adhesive layer 121 to maintain therigidity of the lighting apparatus 100. To this end, the metal film 122may be formed of copper (Cu) having a thickness of 20 μm but is notlimited thereto and may vary in various forms depending on the necessityof the design of the lighting apparatus 100.

The protective film 123 is disposed on the metal film 122 to absorb theexternal impact of the lighting apparatus 100 and protect the lightingapparatus 100. To this end, the protective film 123 may be formed of apolyethylene terephthalate (PET) film which is a polymer film having athickness of 100 μm but is not limited thereto and may vary in variousforms depending on the necessity of the design of the lighting apparatus100.

FIG. 2 is a cross-sectional view illustrating a stack structure of anorganic layer according to an exemplary aspect of the presentdisclosure;

Specifically, FIG. 2 illustrates an organic layer 116 having a tandemstructure including a triple stack.

Referring to FIG. 2, the organic layer 116 includes a first stack ST1including a first organic light emitting layer EML1, a second stack ST2including a second organic light emitting layer EML2, a third stack ST3including a third organic light emitting layer EML3, a first chargegenerating layer CGL1 disposed between the first stack ST1 and thesecond stack ST2, and a second charge generating layer CGL2 disposedbetween the second stack ST2 and the third stack ST3, in the disposedorder on the first electrode 115.

The first charge generating layer CGL1 includes a first N-type chargegenerating layer N-CGL1 and a first P-type charge generating layerP-CGL1 and the first N-type charge generating layer N-CGL1 is in contactwith the second electron transport layer ETL2. The first P-type chargegenerating layer P-CGL1 is disposed between the first N-type chargegenerating layer N-CGL1 and the first hole transport layer HTL1.

The second charge generating layer CGL2 includes a second N-type chargegenerating layer N-CGL2 and a second P-type charge generating layerP-CGL2 and the second N-type charge generating layer N-CGL2 is incontact with the third electron transport layer ETL3. The second P-typecharge generating layer P-CGL2 is disposed between the second N-typecharge generating layer N-CGL2 and the second hole transport layer HTL2.

The first and second charge generating layers CGL1 and CGL2 may beconfigured by a plurality of layers including first and second N-typecharge generating layers N-CGL1 and N-CGL2 and first and second P-typecharge generating layers P-CGL1 and P-CGL2, respectively, but it is notlimited thereto and may be configured by a single layer.

The first N-type charge generating layer N-CGL1 injects electrons to asecond stack ST2 and the second N-type charge generating layer N-CGL2injects electrons to a third stack ST3. The first N-type chargegenerating layer N-CGL1 and the second N-type charge generating layerN-CGL2 may include an N-type dopant material and an N-type hostmaterial, respectively. The N-type dopant material may be a metal ofGroup 1 and Group 2 on the periodic table, an organic material which mayinject the electrons, or a mixture thereof. For example, the N-typedopant material may be any one of an alkali metal and an alkaline earthmetal. Or, the first N-type charge generating layer N-CGL1 may be formedof the organic layer 116 doped with an alkali metal such as lithium(Li), sodium (Na), potassium (K), or cesium (Cs) or an alkali earthmetal such as magnesium (Mg), strontium (Sr), barium (Ba), or radium(Ra), but is not limited thereto. The N-type host material may be formedof a material which is capable of transmitting electrons, for example,may be formed of any one or more of Alq₃(tris(8-hydroxyquinolino)aluminum), Lig(8-hydroxyquinolinolato-lithium),PBD(2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole),TAZ(3-(4-biphenyl)4-phenyl-5-tert-butylphenyl-1,2,4-triazole),spiro-PBD, andBAlq(bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminium), SAlq,TPBi(2,2′,2-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole),oxadiazole, triazole, phenanthroline, benzoxazole, and benzthiazole, butis not limited thereto.

The first P-type charge generating layer P-CGL1 injects holes to thefirst stack ST1 and the second P-type charge generating layer P-CGL2injects holes to the second stack ST2. The first P-type chargegenerating layer P-CGL1 and the second P-type charge generating layerP-CGL2 may include a P-type dopant material and a P-type host material.The P-type dopant material may be formed of metal oxide such as V₂O₅,MoOx, and WO₃, an organic material such astetrafluoro-tetracyanoquinodimethane (F4-TCNQ), HAT-CN(Hexaazatriphenylene-hexacarbonitrile), or hexaazatriphenylene, but isnot limited thereto. The P-type host material may be formed of amaterial which is capable of transmitting holes, for example, may beformed of a material including any one or more ofNPD(N,N-dinaphthyl-N,N′-diphenylbenzidine)(N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine),TPD(N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine), andMTDATA(4,4′,4-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine), butis not limited thereto.

Each stack structure will be described. The first stack ST1 includes anelectron injection layer EIL, a first electron transport layer ETL1, afirst organic light emitting layer EML1, a first electron blocking layerEBL1, and a first hole transport layer HTL1. The second stack ST2includes a second electron transport layer ETL2, a second organic lightemitting layer EML2, a second electron blocking layer EBL2, and a secondhole transport layer HTL2. The third stack ST3 includes a third electrontransport layer ETL3, a third organic light emitting layer EML3, a thirdelectron blocking layer EBL3, a third hole transport layer HTL3, and ahole injection layer HIL.

The hole injection layer HIL is an organic layer which smoothly injectsthe hole from the second electrode 117 to the third organic lightemitting layer EML3. The hole injection layer HIL may be formed of amaterial including any one or more ofHAT-CN(dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10.11-hexacarbonitrile),CuPc (phthalocyanine),F4-TCNQ(2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane), andNPD(N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine),but is not limited thereto.

The first to third hole transport layers HTL1, HTL2, and HTL3 areorganic layers which smoothly transmit holes to the first to thirdorganic light emitting layers EML1, EML2, and EML3. For example, thefirst to third hole transport layers HTL1, HTL2, and HTL3 may be formedof a material including any one or more ofNPD(N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine),TPD(N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine),s-TAD(2,2′,7,7′-tetrakis(N,N-dimethylamino)-9,9-spirofluorene), andMTDATA(4,4′,4″-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine),but is not limited thereto.

The first to third electron blocking layers EBL1, EBL2, and EBL3 areorganic layers which block the electrons injected to the first to thirdorganic light emitting layers EML1, EML2, and EML3 from passing over thefirst to third hole transport layers HTL1, HTL2, and HTL3. The first tothird electron blocking layers EBL1, EBL2, and EBL3 improve the couplingof the holes and electrons in the first to third organic light emittinglayers EML1, EML2, and EML3 by blocking the movement of the electronsand improve the emission efficiency of the first to third organic lightemitting layers EML1, EML2, and EML3. The first to third electronblocking layers EBL1, EBL2, and EBL3 may be formed of the same materialas the first to third hole transport layers HTL1, HTL2, and HTL3. Thefirst to third hole transport layers HTL1, HTL2, and HTL3 and the firstto third electron blocking layers EBL1, EBL2, and EBL3 may be formed asseparate layers. However, the present disclosure is not limited theretoand the first to third hole transport layers HTL1, HTL2, and HTL3 andthe first to third electron blocking layers EBL1, EBL2, and EBL3 may becombined.

In the first to third organic light emitting layers EML1, EML2, andEML3, the holes supplied through the first electrode 115 and theelectrons supplied through the second electrode 117 are recombined togenerate excitons. Here, an area where the excitons are generated isreferred to as an emission area (or emission zone) or a recombinationzone.

The first to third organic light emitting layers EML1, EML2, and EML3are disposed between the first to third hole transport layers HTL1,HTL2, and HTL3 and the first to third electron transport layers ETL1,ELT2, and ELT3 and include a material which emits specific coloredlight. For example, in the lighting apparatus 100 according to theexemplary aspect of the present disclosure, the first organic lightemitting layer EML1 may include a material which emits green light, thesecond organic light emitting layer EML2 may include a material whichemits blue light, and the third organic light emitting layer EML3 mayinclude a material which emits red light.

Here, each of the organic light emitting layers EML1, EML2, and EML3 mayhave a host-dopant system, that is, a system in which a host materialhaving a large weight ratio is doped with an emission dopant materialhaving a small weight ratio. In this case, each of the organic lightemitting layers EML1, EML2, and EML3 may include a plurality of hostmaterials or include a single host material.

For example, in the first organic light emitting layer EML1, a greenphosphorescent dopant material is doped. That is, the first organiclight emitting layer EML1 is a green light emitting layer and a range ofa wavelength of light emitted from the first organic light emittinglayer EML1 may be 570 nm to 490 nm.

Specifically, the first organic light emitting layer EML1 includes ahost material including carbazole biphenyl (CBP) ormCP(1,3-bis(carbazol-9-yl) and may further include a phosphorescentdopant material including Ir(ppy)3(fac tris(2-phenylpyridine)iridium),Ir(ppy)2(acac), or Ir(mpyp)3, but it is not limited thereto.

Further, in the second organic light emitting layer EML2, a bluephosphorescent dopant material is doped. That is, the second organiclight emitting layer EML2 is a blue light emitting layer and a range ofa wavelength of light emitted from the second organic light emittinglayer EML2 may be 490 nm to 450 nm.

Specifically, the second organic light emitting layer EML2 may include ahost material including CBP (carbazole biphenyl) or mCP(1,3-bis(carbazol-9-yl) and may further include a fluorescent dopantmaterial including any one selected from a group consisting ofspiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFObased polymer, and PPV based polymer, but is not limited thereto.

In the third organic light emitting layer EML3, a red phosphorescentdopant material is doped. That is, the third organic light emittinglayer EML3 is a red light emitting layer and a range of a wavelength oflight emitted from the third organic light emitting layer EML3 may be720 nm to 640 nm.

Specifically, the third organic light emitting layer EML3 includes ahost material including carbazole biphenyl (CBP) ormCP(1,3-bis(carbazol-9-yl)) and may further include a phosphorescentdopant material which includes one or more selected from a groupconsisting of PIQIr(acac)(bis(1-phenylisoquinoline)acetylaetonateiridium, PQIr(acac)(bis(1-phenylquinoline)acetylacetonate iridium),PQIr(tris(1-phenylquinoline) iridium), and PtOEP(octaethylporphyrinplatinum), but is not limited thereto.

The first to third electron transport layers ETL1, ELT2, and ETL3transmit the electrons from the electron injection layer EIL and thefirst and second N-type charge generating layers N-CGL1 and N-CGL2 tothe organic light emitting layer EML.

Further, the first to third electron transport layers ETL1, ETL2, andETL3 perform the same function as a hole blocking layer HBL. The holeblocking layer HBL may suppress the holes which do not participate inthe recombination from being leaked from the organic light emittinglayer EML.

For example, the first to third electron transport layers ETL1, ETL2,and ETL3 may be formed of any one or more ofLig(8-hydroxyquinolinolato-lithium),PBD(2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole),TAZ(3-(4-biphenyl)4-phenyl-5-tert-butylphenyl-1,2,4-triazole),BCP(2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline), and BAlq(bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminum), but is notlimited thereto.

The electron injection layer EIL is a layer which smoothly injects theelectron from the first electrode 115 to the first organic lightemitting layer EML1. For example, the electron injection layer EIL maybe formed of a material including any one or more of alkali metals oralkaline earth metal ions, such as LiF, BaF2, and CsF, but is notlimited thereto.

The electron injection layer EIL and the electron transport layer ETLmay be omitted depending on a structure or a characteristic of thelighting apparatus 100 using an organic light emitting diode.

FIG. 3A is a front view of a lighting apparatus using an organic lightemitting diode according to an exemplary aspect of the presentdisclosure. FIG. 3B is an enlarged view of a lighting unit of a lightingapparatus using an organic light emitting diode according to anexemplary aspect of the present disclosure.

FIG. 4 is a cross-sectional view taken along line I-I′ of FIG. 3A.

Specifically, FIG. 3A illustrates an arrangement relationship of thefirst electrode 115, the second electrode 117, and the encapsulatingunit 120. FIG. 4 explains a connection relationship of the secondelectrode 117 and a second contact electrode 117 p and a connectionrelationship of the first electrode 115 and a first contact electrode115 p.

As illustrated in FIGS. 3A and 4, the first electrode 115 is disposed onthe substrate 111, the second electrode 117 is disposed on the firstelectrode 115, and the encapsulating unit 120 is disposed so as to coverthe second electrode 117.

Here, the overlapping area of the first electrode 115 and the secondelectrode 117 may be defined as a lighting unit EA where light isgenerated from the organic layer 116 disposed between the firstelectrode 115 and the second electrode 117.

In other words, the lighting apparatus 100 according to the presentdisclosure may be divided into a lighting unit EA which actually emitslight to the outside and pad units PA1 and PA2 which are electricallyconnected to the outside through the first and second contact electrodes115 p and 117 p to apply a signal to the lighting unit EA.

The pad units PA1 and PA2 are not blocked by the encapsulation unit suchas a metal film 122 so that the pad units PA1 and PA2 may beelectrically connected to the outside through the first and secondcontact electrodes 115 p and 117 p. Therefore, the metal film 122 may beattached onto the entire surface of the lighting unit EA of thesubstrate 111 excluding the pad units PA1 and PA2. However, the presentdisclosure is not limited thereto.

That is, in the pad units PA1 and PA2 at the outer edge of the lightingunit EA, the organic layer 116, the second electrode 117, the adhesivelayer 121, and the metal film 122 are not formed so that the first andsecond contact electrodes 115 p and 117 p are exposed to the outside.

The pad units PA1 and PA2 may be located outside the lighting unit EA.In FIG. 3A, even though it is illustrated that the second pad unit PA2is located between the first pad units PA1, the present disclosure isnot limited thereto.

Further, in FIG. 3A, even though it is illustrated that the pad unitsPA1 and PA2 are located only at one outer side of the lighting unit EA,the present disclosure is not limited thereto. Therefore, the pad unitsPA1 and PA2 of the present disclosure may be disposed in both one outerside and the other outer side of the lighting unit EA. Further, thefirst pad unit PA1 of the present disclosure may be located at one outerside of the lighting unit EA and the second pad unit PA2 may be locatedat the other outer side of the lighting unit EA.

With regard to this, the first contact electrode 115 p disposed in thefirst pad unit PA1 is formed of the same material on the same layer asthe first electrode 115 disposed in the lighting unit EA. Therefore, thefirst contact electrode 115 p is formed by the same process when thefirst electrode 115 is formed, to be electrically connected to the firstelectrode 115.

The second contact electrode 117 p disposed in the second pad unit PA2is formed of the same material on the same layer as the first electrode115 disposed in the lighting unit EA by the same process. However, thesecond contact electrode 117 p is separated from the first electrode 115and the auxiliary line AL which is electrically connected to the firstelectrode 115 and is electrically connected to the second electrode 117through a connecting hole CNT.

Specifically, as illustrated in FIG. 4, the first contact electrode 115p is connected to the first electrode 115 and the auxiliary line AL toform an equipotential surface with the first electrode 115. Therefore,the first contact electrode 115 p, the auxiliary line AL, and the firstelectrode 115 are electrically connected to each other. Further, thesecond contact electrode 117 p is electrically connected to the secondelectrode 117 and a dummy electrode DM.

The above-mentioned dummy electrode DM is formed of the same material onthe same layer as the auxiliary line AL, but is electrically isolatedfrom the auxiliary line AL. Therefore, the first electrode 115 and thesecond electrode 117 are not electrically connected.

With this connection structure, the first contact electrode 115 pdisposed in the first pad unit PA1 may transmit a signal applied fromthe outside to the first electrode 115. Further, the second contactelectrode 117 p disposed in the second pad unit PA2 may transmit thesignal applied from the outside to the second electrode 117.

In the meantime, the first electrode 115 is formed of a transparentconductive layer to have an advantage in that the emitted lighttransmits the first electrode, but also have a disadvantage in that anelectric resistance is very high as compared with an opaque metal.Therefore, when a large-size lighting apparatus 100 is manufactured, thedistribution of the current applied to a large lighting unit EA is notuniform due to high resistance of the transparent high resistiveconductive layer. Therefore, the large-size lighting apparatus cannotemit light with uniform luminance due to the current distribution whichis not uniform.

Therefore, as illustrated in FIGS. 3B and 4, for the purpose of emissionwith uniform luminance of the large-size lighting apparatus 100, anauxiliary line AL may be disposed, which is electrically connected tothe first electrode 115 and makes the distribution of current applied tothe lighting unit EA uniform.

The auxiliary line AL is disposed over the entire lighting unit EA witha net shape, a mesh shape, a hexagonal or octagonal shape, or a circularshape having a small thickness. The auxiliary line AL may be formed of ametal having good conductivity such as aluminum (Al), gold (Au), copper(Cu), titanium (Ti), tungsten (W), molybdenum (Mo), or an alloy thereof.Even though not illustrated in the drawing, the auxiliary line AL may beconfigured to have a double stack structure of an upper auxiliary lineAL and a lower auxiliary line AL, but the present disclosure is notlimited thereto, and the auxiliary line may be configured by a singlestack.

Here, in FIG. 4, it is illustrated that the auxiliary line AL which iselectrically connected to the first electrode 115 is disposed below thefirst electrode 115 to be in electrical contact with the first electrode115. However, the present disclosure is not limited thereto, and theauxiliary line AL may be disposed above the first electrode 115.

Further, as illustrated in FIGS. 3B and 4, a short reduction pattern SRis formed in the first electrode 115, to which the current is supplied,to implement a narrow path and the insulating layer INS covers the shortreduction pattern SR to suppress the short of the entire panel. That is,the short reduction pattern SR is formed to enclose an outer edge of theemission area of the individual pixel and make the part of the anodeinside the short reduction pattern and the part of the anode outside theshort reduction pattern connect to each other through a narrow path, andthus adds a resistance to the individual pixels to restrict currentflowing in an area where the short is generated.

An insulating layer INS is disposed between the first electrode 115 andthe second electrode 117 where the auxiliary line AL of the lightingunit EA is disposed to suppress the short between the first electrode115 and the second electrode 117 due to the damage of the organic layer116.

Specifically, the insulating layer INS is configured to cover theauxiliary line AL and the first electrode 115. As described above, theinsulating layer INS is formed so as to enclose the auxiliary line AL toreduce the step due to the auxiliary line AL. Therefore, various layerswhich are formed on the insulating layer INS thereafter may be stablyformed without being shorted.

Here, the insulating layer INS may be configured by an inorganicmaterial such as silicon oxide SiOx or silicon nitride SiNx. However,the insulating layer INS may be configured by an organic layer such asphotoacryl PAC and also configured by a plurality of layers of inorganiclayers and organic layers.

Hereinafter, an arrangement relationship of an organic light emittinglayer of a lighting apparatus including an organic light emitting diodeaccording to an exemplary aspect of the present disclosure will bedescribed in detail with reference to FIGS. 5 and 6.

FIG. 5 is a view for explaining a relationship of a degree of horizontalorientation of a dopant and a light loss at an interface of an organiclayer and a second electrode.

As described above, in the lighting apparatus using an organic lightemitting diode according to an exemplary aspect of the presentdisclosure, the third organic light emitting layer EML3 which is a redphosphorescent light emitting layer, the second organic light emittinglayer EML2 which is a blue fluorescent light emitting layer, and thefirst organic light emitting layer EML1 which is a green phosphorescentlight emitting layer are disposed in this order from the secondelectrode 117.

That is, the lighting apparatus 100 using an organic light emittingdiode according to an exemplary aspect of the present disclosureincludes the first organic light emitting layer EML1 and the thirdorganic light emitting layer EML3 which are phosphorescent lightemitting layers and the second organic light emitting layer EML2 whichis a fluorescent light emitting layer.

Here, the first organic light emitting layer EML1 may be defined as afirst phosphorescent light emitting layer and the third organic lightemitting layer EML3 may be defined as a second phosphorescent lightemitting layer.

Here, the fluorescent light emitting layer emits light by singletexcitons so that an internal quantum efficiency (IQE) is 25%. Incontrast, the phosphorescent light emitting layer emits light by tripletexcitons so that the internal quantum efficiency (IQE) is 100%.

However, in the case of the fluorescent light emitting layer, theinternal quantum efficiency (IQE) is increased using delayedfluorescence. However, generally, the internal quantum efficiency (IQE)of the phosphorescent light emitting layer is twice of the internalquantum efficiency (IQE) of the fluorescent light emitting layer, sothat the emission efficiency of the lighting apparatus 100 using anorganic light emitting diode is determined by the emission efficiency ofthe phosphorescent light emitting layer.

Therefore, hereinafter, after explaining an arrangement relationship ofthe first organic light emitting layer EML1 and the third organic lightemitting layer EML3 which are phosphorescent light emitting layers, thearrangement relationship of the second organic light emitting layer EML2which is a fluorescent light emitting layer will be described.

A degree of horizontal orientation of a red phosphorescent dopantincluded in the third organic light emitting layer EML3 is higher than adegree of horizontal orientation of the green phosphorescent dopantincluded in the first organic light emitting layer EML1. For example,the degree of horizontal orientation of the red phosphorescent dopantincluded in the third organic light emitting layer EML3 may be 87% andthe degree of horizontal orientation of the green phosphorescent dopantincluded in the first organic light emitting layer EML1 may be 75%.

Here, the degree of horizontal orientation of the dopant refers to adegree of an average horizontal orientation of a dipole direction of thedopant with respect to a reference plane when an interface of theorganic layer 116 and the second electrode 117 which is a reflectiveelectrode is set as a reference plane.

That is, as illustrated in FIG. 5, when a dipole direction of a firstdopant DP1 is vertical to the reference plane, a degree of horizontalorientation of the first dopant DP1 is 0%. When a dipole direction of asecond dopant DP2 is horizontal to the reference plane, a degree ofhorizontal orientation of the second dopant DP2 is 100%.

A surface plasmon polariton (SPP) loss at the interface of the organiclayer 116 and the second electrode 117 which is a reflective electrodewill be described based on them.

First, in the case of the first dopant DP1 having a degree of horizontalorientation of 0%, the generated light (electromagnetic wave) travels ina horizontal direction of the interface of the organic layer 116 and thesecond electrode 117. Therefore, the light is coupled to surface plasmonwhich is a vibration of free electrons on the interface to be in asurface plasmon polariton (SPP) state. The more the surface plasmonpolariton (SPP), the more the loss by the second electrode 117.Therefore, the emission efficiency of light generated by the firstdopant DPI having a low degree of horizontal orientation is lowered.

In contrast, in the case of the second dopant DP2 having a degree ofhorizontal orientation of 100%, the generated light (electromagneticwave) travels in a vertical direction of the interface of the organiclayer 116 and the second electrode 117. Therefore, the light isreflected by the second electrode 117 which is a reflective electrode sothat the light loss is not caused by the surface plasmon polariton (SPP)state and the light is extracted to the outside. Therefore, the emissionefficiency of the light generated by the second dopant DP2 having a highdegree of horizontal orientation is improved.

As a result, only when a phosphorescent light emitting layer having ahigh degree of horizontal orientation, among the plurality ofphosphorescent light emitting layers, is disposed to be adjacent to thesecond electrode 117, the light loss by the surface plasmon polariton(SPP) state is minimized. Therefore, the entire emission efficiency ofthe lighting apparatus 100 is improved.

Therefore, as described above, the degree of horizontal orientation ofthe red phosphorescent dopant included in the third organic lightemitting layer EML3 is higher than the degree of horizontal orientationof the green phosphorescent dopant included in the first organic lightemitting layer EML1. Therefore, the third organic light emitting layerEML3 may be disposed to be more adjacent to the second electrode 117which is a reflective electrode than the first organic light emittinglayer EML1.

FIG. 6 is a graph illustrating luminous efficiency depending on adistance between an organic light emitting layer and a second electrode.

Referring to FIG. 6, the first, the second and the third organic lightemitting layers each has a first emission efficiency peak at a firstdistance from the cathode and a second emission efficiency peak at asecond distance from the cathode. The maximum emission efficiency of thefirst organic light emitting layer EML1 represented by a one-dot chainline is 105 W/m² and maximum emission efficiency of the third organiclight emitting layer EML3 represented by a two-dot chain line is 110W/m². Therefore, the third organic light emitting layer EML3 havinghigher maximum emission efficiency is disposed to be most adjacent tothe second electrode 117 so that the entire efficiency of the lightingapparatus 100 using an organic light emitting diode according to anexemplary aspect of the present disclosure may be improved.

Referring to FIG. 2, a distance D3 from a bottom surface of the secondelectrode 117 to a top surface of the third organic light emitting layerEML3 is 900 Å to 1200 Å, at which the first emission efficiency peak ofthe third organic light emitting layer EML3 is located.

The first organic light emitting layer EML1 may be disposed in thesection of 2600 Å to 2900 Å which is a position representing a secondmaximum emission efficiency of 90 W/m². That is, a distance D1 from thebottom surface of the second electrode 117 to a top surface of the firstorganic light emitting layer EML1 is 2600 Å to 2900 Å, at which thesecond emission efficiency peak of the first organic light emittinglayer EML1 is located.

Separately, the second organic light emitting layer EML2 which is theblue fluorescent organic light emitting layer has maximum emissionefficiency of 27 W/m² in a position spaced apart from the secondelectrode by 700 Å. However, in this arrangement section, the thirdorganic light emitting layer EML3 is disposed as described above so thatthe second organic light emitting layer EML2 may be disposed in asection of 1700 Å to 2000 Å which represents second maximum emissionefficiency of 23 W/m². That is, a distance D2 from the bottom surface ofthe second electrode 117 to the top surface of the second organic lightemitting layer EML2 is 1700 Å to 2000 Å, at which the second emissionefficiency peak of the second organic light emitting layer EML2 islocated.

In summary, the third organic light emitting layer EML3 which is a redphosphorescent light emitting layer having a high degree of horizontalorientation is disposed in a distance of 900 Å to 1200 Å from the secondelectrode 117. The second organic light emitting layer EML2 which is ablue fluorescent light emitting layer is disposed in a distance of 1700Å to 2000 Å from the second electrode 117. Further, the first organiclight emitting layer EML1 which is a green phosphorescent light emittinglayer having a low degree of horizontal orientation is disposed in adistance of 2600 Å to 2900 Å from the second electrode 117. Therefore,the loss of the surface plasmon polariton (SPP) state of the lightingapparatus 100 using an organic light emitting diode according to anexemplary aspect of the present disclosure is minimized, therebyimproving the entire emission efficiency.

The exemplary aspects of the present disclosure can also be described asfollows:

According to an aspect of the present disclosure, a lighting apparatususing an organic light emitting diode includes: a substrate; a firstelectrode disposed on the substrate; an organic layer which is disposedon the first electrode and includes a plurality of phosphorescent lightemitting layers; and a second electrode disposed on the organic layer,and a phosphorescent light emitting layer having a highest degree ofhorizontal orientation of a dopant among the plurality of phosphorescentlight emitting layers is disposed to be adjacent to the secondelectrode. Therefore, the emission efficiency of the lighting apparatusmay be improved.

The second electrode is formed of a reflective metal.

The organic layer further includes at least one fluorescent lightemitting layer.

The plurality of phosphorescent light emitting layers includes a firstphosphorescent light emitting layer and a second phosphorescent lightemitting layer having a dopant having a higher degree of horizontalorientation than that of the first phosphorescent light emitting layer,the first phosphorescent light emitting layer is disposed on the firstelectrode, at least one fluorescent light emitting layer is disposed onthe first phosphorescent light emitting layer, the second phosphorescentlight emitting layer is disposed on the at least one fluorescent lightemitting layer, and the second electrode is disposed on the secondphosphorescent light emitting layer.

The first phosphorescent light emitting layer may emit green light, theat least one fluorescent light emitting layer may emit blue light, andthe second phosphorescent light emitting layer may emit red light.

A distance between a bottom surface of the second electrode and a topsurface of the first phosphorescent light emitting layer may range from2600 Å to 2900 Å.

A distance between a bottom surface of the second electrode and a topsurface of the second phosphorescent light emitting layer may range from900 Å to 1200 Å.

A distance between a bottom surface of the second electrode and the atleast one fluorescent light emitting layer may range from 1700 Å to 2000Å.

The first electrode may include a short reduction pattern whichimplements a narrow path.

According to another aspect of the present disclosure, a lightingapparatus using a three-stack tandem type organic light emitting diode,a first stack adjacent to a transparent electrode includes a greenphosphorescent light emitting layer, a third stack adjacent to areflective electrode includes a red phosphorescent light emitting layer,and a second stack disposed between the first stack and the third stackincludes a blue fluorescent light emitting layer. Therefore, theemission efficiency of the lighting apparatus may be improved.

A degree of horizontal orientation of a dopant of the red phosphorescentlight emitting layer may be higher than that of the green phosphorescentlight emitting layer.

A distance between a bottom surface of the reflective electrode and atop surface of the green phosphorescent light emitting layer may rangefrom 2600 Å to 2900 Å.

A distance between a bottom surface of the reflective electrode and atop surface of the red phosphorescent light emitting layer may rangefrom 900 Å to 1200 Å.

A distance between a bottom surface of the reflective electrode and theblue fluorescent light emitting layer may range from 1700 Å to 2000 Å.

What is claimed is:
 1. An organic light emitting diode, comprising: ananode; an organic layer disposed on the anode and including a pluralityof phosphorescent light emitting layers; and a cathode disposed on theorganic layer, wherein a phosphorescent light emitting layer having ahighest degree of horizontal orientation of a dopant among the pluralityof phosphorescent light emitting layers is disposed to be adjacent tothe cathode, and wherein the anode includes a short reduction patternwhich implements a narrow path.
 2. The organic light emitting diodeaccording to claim 1, wherein the cathode is formed of a reflectivemetal.
 3. The organic light emitting diode according to claim 1, whereina distance between a bottom surface of the cathode and a top surface ofthe phosphorescent light emitting layer having a highest degree ofhorizontal orientation of a dopant ranges from 900 Å to 1200 Å.
 4. Theorganic light emitting diode according to claim 1, further comprising aphosphorescent light emitting layer having a second highest degree ofhorizontal orientation of dopant among the plurality of phosphorescentlight emitting layers, wherein the phosphorescent light emitting layerhaving a second highest degree of horizontal orientation of a dopant isdisposed to be adjacent to the anode.
 5. The organic light emittingdiode according to claim 4, wherein a distance between a bottom surfaceof the cathode and a top surface of the phosphorescent light emittinglayer having a second highest degree of horizontal orientation of adopant ranges from 2600 Å to 2900 Å.
 6. The organic light emitting diodeaccording to claim 4, further comprising a fluorescent light emittinglayer disposed between the phosphorescent light emitting layer havingthe highest degree of horizontal orientation of a dopant and thephosphorescent light emitting layer having the second highest degree ofhorizontal orientation of a dopant.
 7. The organic light emitting diodeaccording to claim 6, wherein a distance between a bottom surface of thecathode and a top surface of the fluorescent light emitting layer rangesfrom 1700 Å to 2000 Å.
 8. The organic light emitting diode according toclaim 6, wherein the phosphorescent light emitting layer having thehighest degree of horizontal orientation of a dopant is a redphosphorescent light emitting layer, the phosphorescent light emittinglayer having the second highest degree of horizontal orientation of adopant is a green phosphorescent light emitting layer, and theflorescent light emitting layer is a blue florescent light emittinglayer.
 9. The organic light emitting diode according to claim 1, whereinthe short reduction pattern encloses an outer edge of the emission areaof a pixel and makes the part of the anode inside the short reductionpattern and the part of the anode outside the short reduction patternconnect to each other through the narrow path.
 10. A lighting apparatus,comprising the organic light emitting diode according to claim
 1. 11. Anorganic light emitting diode, comprising: an anode; an organic layerdisposed on the anode and including a first and a second phosphorescentlight emitting layers; and a cathode disposed on the organic layer,wherein the first and the second phosphorescent light emitting layerseach has a first emission efficiency peak at a first distance from thecathode and a second emission efficiency peak at a second distance fromthe cathode, wherein the first distance of the first phosphorescentlight emitting layer is smaller than the first distance of the secondphosphorescent light emitting layer.
 12. The organic light emittingdiode according to claim 11, further comprising a fluorescent lightemitting layer disposed between the first and the second phosphorescentlight emitting layers, wherein the fluorescent light emitting layer hasthe first emission efficiency peak at the first distance from thecathode and the second emission efficiency peak at the second distancefrom the cathode.
 13. The organic light emitting diode according toclaim 12, wherein a position of the second emission efficiency peak ofthe fluorescent light emitting layer is located between a position ofthe first emission efficiency peak of the first phosphorescent lightemitting layer and a position of the second emission efficiency peak ofthe first phosphorescent light emitting layer.
 14. The organic lightemitting diode according to claim 12, wherein the position of the secondemission efficiency peak of the fluorescent light emitting layer islocated between the position of the first emission efficiency peak ofthe second phosphorescent light emitting layer and the position of thesecond emission efficiency peak of the second phosphorescent lightemitting layer.
 15. The organic light emitting diode according to claim11, wherein the cathode is formed of a reflective metal.
 16. The organiclight emitting diode according to claim 12, wherein the firstphosphorescent light emitting layer emits red light, the fluorescentlight emitting layer emits blue light, and the second phosphorescentlight emitting layer emits green light.
 17. The organic light emittingdiode according to claim 12, wherein a distance between a bottom surfaceof the cathode and a top surface of the first phosphorescent lightemitting layer ranges from 900 Å to 1200 Å, at which the first emissionefficiency peak of the first phosphorescent light emitting layer islocated.
 18. The organic light emitting diode according to claim 12,wherein a distance between a bottom surface of the cathode and a topsurface of the second phosphorescent light emitting layer ranges from2600 Å to 2900 Å, at which the second emission efficiency peak of thesecond phosphorescent light emitting layer is located.
 19. The organiclight emitting diode according to claim 12, wherein a distance between abottom surface of the cathode and the fluorescent light emitting layerranges from 1700 Å to 2000 Å, at which the second emission efficiencypeak of the fluorescent light emitting layer is located.
 20. The organiclight emitting diode according to claim 11, wherein the anode includes ashort reduction pattern which implements a narrow path.